The construction phase of sports buildings is characterized by high carbon emission intensity, yet existing studies have largely focused on operational energy consumption and static life-cycle accounting, with no systematic investigation of the dynamic interactions among labor, materials, machinery, and environmental factors during construction. To fill this gap, this study develops an agent-based modeling (ABM) framework for a university natatorium in Shaanxi, China, to assess carbon emissions during the civil engineering construction phase and analyzes the independent and synergistic effects of labor, materials, machinery, and environmental factors. The simulation results show that, among single factors, material recycling achieves the highest reduction efficiency (57.93%, under the avoided-burden approach, representing a technical upper-bound estimate), followed by labor skill improvement (3.08%) and machinery maintenance (0.26%), while adverse weather increases carbon emissions by 13.20%. Multi-factor synergy analysis reveals that labor skill improvement buffers weather-induced increases (synergy: +610.49 t, 4.26%), and the full-intervention scenario achieves a 52.33% net reduction under adverse weather, though weather impacts cannot be fully offset. The proposed framework provides methodological support and a decision-making basis for low-carbon construction planning of natatoriums and similar buildings.

To fill the research gap of green building assessment theory being underutilized in sports architecture and advance the use of life-cycle assessment (LCA) for complex public building types, this study develops a comprehensive life-cycle green evaluation indicator system specifically for public sports venues. First, the factors influencing green performance were systematically identified across four life-cycle stages—planning and design, construction, operation and maintenance, and end-of-life—leading to the establishment of an initial indicator pool. This pool was subsequently refined through a two-round Delphi expert consultation. The weights of the indicators were then determined using a combined Analytic Hierarchy Process (AHP) and Entropy Weight Method (EWM) approach to quantify the relative importance of each indicator. The resulting framework comprises a comprehensive green evaluation indicator system for the whole life cycle of public sports venues, consisting of 4 first-level, 12 second-level, and 28 third-level indicators. The results reveal a pronounced front-loaded influence in the life-cycle weight distribution, indicating that decisions made during the planning and design stage are most critical for the green performance of sports venues. Based on the weight distribution characteristics, this study further delineates a phase-specific governance logic for green development: the planning and design stage should prioritize design optimization to maximize life-cycle green performance potential; the construction stage should focus on controlling resource input and process carbon emissions; the operation and maintenance stage should emphasize energy consumption optimization and resource recycling; and the end-of-life stage should address resource regeneration. This study not only extends green building assessment and life-cycle assessment theories to sports architecture—a complex and under-researched building typology—but also provides stakeholders with a robust decision-support tool to advance the sustainable development of public sports venues.